1. Field of the Invention
The present invention relates generally to crop harvesters, and more particularly to such a harvester which is adapted to travel along a row of crops, and to engage said crops and bring them more closely together to enhance the harvesting operation of the crops.
2. Background Art
There are in the prior art harvesting machines which are adapted to harvest such crops as berries, grapes, fruit, other produce from standing plants. Normally such machines comprise a chassis having two side portions which define therebetween a crop engaging area. As the machine travels down a crop row, the crops pass between the two side portions of the machine, and suitable harvesting implements, such as beater rods or the like engage the crop to shake the crop and thus cause removal of the berries or other food product.
It has been found that this harvesting operation can be enhanced if the lower portions of the crops or plants can be engaged so as to squeeze the lower portions of the crops toward the row centerline. Accordingly, one prior art device for accomplishing this is to have two crop engaging belts positioned on opposite sides of the crop, with these belts being urged toward a center location so as to engage the crops with the appropriate pressure. These two belts are then driven so that the crop engaging portions thereof travel rearwardly at substantially the same speed as the forward travel of the vehicle, so that the crop engaging belt portions are "stationary" relative to the crop. Thus, there arises a need to coordinate the rearward speed of the belt engaging portions with the forward travel of the machine. Such an aggregating device is disclosed on pages 33 and 34 of a book entitled "Mechanical Harvesting of Raspberries: Development of a System for Scottish Conditions", authored by A. M. Ramsay, published by the Scottish Institute of Agricultural Engineering, Technical Report No. 7. Also, illustrations of this same system are shown in photographs appearing in different parts of this publication.
U.S. Pat. No. 4,204,389 (Delfosse) shows an endless conveyor in a harvester, the conveyor being timed to be stationary relative to the crop.
One means of monitoring the ground speed of the harvesting machine so that the speed of a crop engaging member can be controlled is by actually measuring the forward speed of the machine and then providing control means responsive to the forward speed of the machine. One method of accomplishing this is by means of a ground engaging wheel which engages the ground and thus rotates at a speed proportional to the forward velocity. One such system is shown in U.S. Pat. No. 4,176,511 (Scudder et al), entitled "Conveyor System for a Harvester", where there are shown two conveyors in the form of endless belts which are positioned on opposite sides of the crop row and which travel rearwardly relative to the machine so that these are "stationary" relative to the crop row. With reference to FIGS. 8, 16 and 17, there is a hydraulic motor 30a which rotates the two belt conveyors, with this motor 30a being driven by a motor 49 which powers a pump 50 that in turn delivers hydraulic fluid through a throttle control valve 53 that in turn delivers the hydraulic fluid to the motor 30a. To control the speed of the motor 30a, the hydraulic fluid that passes from the motor 30a is directed through a feedback system to control operation of the throttle valve 53. More specifically, there is an unloaded ground engaging wheel 52, the speed of rotation of which is a measure of the speed of forward travel of the machine. This wheel 52 connects through a shaft 59 to a drive transmission comprising gears 61, 62 and 63. The hydraulic motor 55 which is a positive drive motor driven from the pump 30a rotates a gear 64 which in turn rotates a gear 58 which in turn rotates the case 60 of the differential transmission. When the speed of the hydraulic motor 30a matches the ground speed as indicated by the wheel 52, the rotational speed of the differential casing 60 matches the rotational speed of the shaft 59 so that there is no output from the differential transmission, and the shaft 54 leading to the throttle valve 53 remains stationary. However, when a difference in the two speeds is sensed, the shaft 54 will be cause to rotate to change the setting of the throttle valve 53 so that the ground speed does match the speed of the hydraulic motor 30a that in turn drives the belt conveyors. One of the problems of this type of system is that not only must the operating components be closely matched, but there is some margin of error in that the ground wheel (such as a ground wheel 52) may not be a truly reliable indication of ground speed. For example, if the ground surface has some irregularities where the ground wheel must travel upwardly and downwardly over the ground surface, the rate of rotation will increase relative to the forward speed of the vehicle. Further, even though these ground wheels can be arranged with devices to increase friction (high friction treads or even pins or the like) which would engage the ground, there can under certain circumstances be slippage of such wheels.
Various other systems and method time the speed of a conveyor or the like to the rotation of a ground wheel, by using a governor responsive to rotation of the ground wheel to control a throttle valve in a hydraulic conveyor drive system, U.S. Pat. No. 3,414,200 (Savory), monitors for monitoring the speed of the conveyor belt and of a vehicle which use electro-optical aperture discs, U.S. Pat. No. 3,550,866 (Swenson), magnetic sensors 46 for sensing and equalizing the speeds of a driven axle and a non-driven axle, U.S. Pat. No. 4,441,848 (Bailey), chains and sprockets, U.S. Pat. Nos. 4,195,570 (Rodriquez) and 3,901,005 (Rohrbach et al) and an intermediate wheel 101 that meshes with a ground wheel and a conveyor to drive the conveyor, U.S. Pat. No. 4,081,094 (Pereira et al). Additionally, U.S. Pat. No. 4,212,428 (Walker) shows a ground wheel that drives a pump 52. The pump 52 provides fluid pressure to operate a motor 36 that drives a conveyor belt.